The present application is based on Japanese Patent Application No. 2001-294929, which is incorporated herein by reference.
1. Field of the Invention
This invention relates to a semi-transmitting reflective plate and a semi-transmitting polarizer to be used in a liquid crystal display (hereinafter sometimes abbreviated as xe2x80x9cLCDxe2x80x9d), and a liquid crystal display using the same.
2. Description of the Related Art
LCDs have been used in desktop computers, electronic watches, personal computers and word processors, and a demand for them has sharply been increased. Thus, production growth of semi-transmitting reflective displays for portable phones and personal portable information terminals is remarkable.
In order to improve display performance of LCD, a semi-transmitting polarizer comprising a polarizer having laminated thereon a semi-transmitting reflective plate is provided usually on the back side of a liquid crystal cell and, as a display method, there has been employed a method in which, in the case of using the liquid crystal display in a comparatively bright atmosphere, an incident light from watching side (display side) is reflected to display an image whereas, in the case of using in a comparatively dark atmosphere, an image is displayed using a built-in light source such as a backlight provided on the back side of the semi-transmitting polarizer. That is, the semi-transmitting polarizer can save energy for a light source such as a backlight under a bright atmosphere, while using a built-in light source under a comparatively dark atmosphere, thus being useful for formation of a liquid crystal display.
However, a recent reduction in thickness of LCD has made the space between respective constituent members so narrow that they are disposed almost close to each other. FIG. 2 is a schematic cross section showing an example of a constitution of a conventional semi-transmitting reflective plate. A semi-transmitting reflective layer 13 comprising a metallic film or a mica-buried resin layer is formed on a light-transmitting high-molecular substrate 11 such as PET, and an adhesive layer 14 is formed on the layer to constitute a semi-transmitting reflective plate 15. The semi-transmitting reflective plate 15 is disposed close to an EL back light 16. Hence, there have been problems that, with a semi-transmitting reflective plate having a smooth back surface, a Newton ring is viewed upon the back light being turned on since the back surface is adsorbed to the surface of an electroluminescence (hereinafter abbreviated as xe2x80x9cELxe2x80x9d) element, and that fine foreign matters sandwiched therebetween are viewed as impact deformation. In addition, there has also been involved a problem of generation of abnormal display due to the sandwiched foreign matters. Further, with the degree of fineness being increased, there has arisen a problem that fine flaws on the back side of the semi-transmitting reflective plate can be viewed upon transmission viewing.
Thus, the present invention is intended to provide a semi-transmitting reflective plate and a semi-transmitting polarizer which can depress generation of Newton ring and can prevent flaws due to the impact deformation or the sandwiched foreign matters, and a liquid crystal display using the same.
In order to solve the problems, the transmitting-reflective plate of the invention has a rough-surfaced layer of 0.1 to 1.0 xcexcm in arithmetic mean roughness and 0.1 to 6.0 xcexcm in average tem-point roughness formed on the back surface of a light-transmitting high-molecular substrate having laminated thereon a semi-transmitting reflective layer.
Also, in the semi-transmitting reflective plate of the invention, the rough-surfaced layer has a surface hardness of preferably H or more.
Also, in the semi-transmitting reflective layer of the invention, the rough-surfaced layer has a peeling strength of preferably 0.5 N/25 mm or more.
Next, the semi-transmitting polarizer of the invention is characterized in that the semi-transmitting reflective plate is laminated on a polarizer.
In addition, the liquid crystal display of the invention is characterized in that the semi-transmitting polarizer is provided on at least one side of a liquid crystal cell. In this liquid crystal display, it is preferred to dispose so that the rough-surfaced layer formed on the semi-transmitting polarizer is on the back side of the display unit of the liquid crystal display.
The arithmetic mean roughness (Ra) and the average ten-point roughness (Rz) in the above description are defined in JIS B0601-1994. As a method for determining these Ra and Rz, there is a method of using, for example, a surface roughness-measuring machine.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.